Apparatus for production of ultrapure amorphous metals utilizing acoustic cooling

Amorphous metals are produced by forming a molten unit of metal and deploying the unit into a bidirectional acoustical levitating field or by dropping the unit through a spheroidizing zone, a slow quenching zone, and a fast quenching zone in which the sphere is rapidly cooled by a bidirectional jet stream created in the standing acoustic wave field produced between a half cylindrical acoustic driver and a focal reflector or a curved driver and a reflector. The cooling rate can be further augmented first by a cryogenic liquid collar and secondly by a cryogenic liquid jacket surrounding a drop tower. The molten unit is quenched to an amorphous solid which can survive impact in a unit collector or is retrieved by a vacuum chuck

Short-term hot hardness characteristics of rolling-element steels

Short-term hot hardness studies were performed with five vacuum-melted steels at temperatures from 294 to 887 K (70 to 1140 F). Based upon a minimum Rockwell C hardness of 58, the temperature limitation on all materials studied was dependent on the initial room temperature hardness and the tempering temperature of each material. For the same room temperature hardness, the short-term hot hardness characteristics were identical and independent of material composition. An equation was developed to predict the short-term hardness at temperature as a function of initial room temperature hardness for AISI 52100, as well as the high-speed tool steels

Optimization of Master Alloy Amount and Gating System Design for Ductile Cast Iron Obtain in Lost Foam Process

The paper presents the optimization of master alloy amount for the high nodular graphite yield (80-90%) in cast iron obtain in lost foam process. The influence of the gating system configuration and the shape of the reaction chamber, the degree of spheroidisation cast iron was examined. Research has shown that the, optimal of master alloy amount of 1.5% by mass on casting iron. The degree of spheroidisation is also influenced by the gating system configuration. The best spheroidisation effect was obtained for liquid cast iron was fed into the reaction chamber from the bottom and discharged from the top

Effect of Ce and Sb on Primary Graphite Growth in Cast Irons

It is well-known that if certain trace elements are present in cast iron melts the morphology of the graphite precipitates can be altered. In order to understand the effect of doping elements on primary growth of graphite, pure Fe–Sb alloys were prepared by induction melting. They were then placed in graphite crucibles and heated to a temperature above the Fe–C eutectic so that the charge became saturated in carbon and melted. To obtain Fe–Ce alloys, metallic Ce was added at the bottom of a graphite crucible and covered with iron, and then heated as for the Fe–Sb charge. In both cases, the melt was then cooled and held slightly above the eutectic temperature so that primary graphite crystals, which had nucleated on the crucible walls and then detached from it, could grow freely in the melt. The influence of the added elements on graphite growth was revealed by the change in the shape and distribution of the crystals compared to those obtained in similar experiments carried out with pure Fe. The experiments were made in air and vacuum so as to point out possible interactions between the elements present in the melt and oxygen

Influence of heating rate on sorbitic transformation temperature of tempering C45 steel

In this paper the analysis of speed heating influence on sorbitic transormation temperature of tempering C45 steel is presented. On thebasis of dilatometric research, functions associating heating time with initial and final temperature of sorbitic transformation have beendetermined as well as the size structural (γ) and thermal (α) expansion coefficients of quenching and tempering structures have beenestimated

Effects of erodant particle shape and various heat treatments on erosion resistance of plain carbon steel

Erosion tests were conducted on 1045 steel samples which had been subjected to different heat treatments. The weight of material removed upon erosion with glass beads and crushed glass was measured. The data show that there is no correlation between hardness and erosion resistance. The erosion rate was strongly dependent on the shape of erodant particles, being an order of magnitude higher for erosion with crushed glass than with glass beads. Heat treatment had a profound effect on the erosion resistance when the erodant particles were glass beads but little or no effect when the particles were crushed glass. It is thus concluded that different mechanisms of material removal are involved with these two erodants. This conclusion is supported by the surface morphology of annealed 1045 steel samples which had been eroded by these two types of erodant particles. SEM micrographs of the eroded surfaces show that for erosion with glass beads it is deformation induced fracture of surface layers

Dilatrometrijska i analiza tvrdoće čelika C45 popuštanog uz različite brzine zagrijavanja

Modelling of technological processes of heat treatment or welding, involving multiple heat source transitions, requires considering the phenomenon of tempering. In work have been presented results of dilatometric research of hardened C45 steel subjected to tempering. The analysis of the influence of heating rate at the kinetic determined from dilatometric curves has been made. There have also been estimated quantities of transformation expansions and thermal expansion coefficients of hardening and tempering structures (austenite, ferrite, pearlite, martensite and sorbite). The analysis of tempering time influence on the hardness of tempered steel has been made. Functions associating hardness with tempering time (rate of heating-up) in technological processes based on short-timed action of a heat source (eg. laser treatment) have been suggested.Modeliranje tehnološkog procesa toplinske obrade ili zagrijavanja, uključivo višedjelne izvore prijelaza topline, zahtijeva razmatranje fenomena toplinske obrade popuštanje. U radu su prezentirani rezultati popuštanja tvrdoće zakaljenog čelika C45. Analiza utjecaja brzine zagrijavanja na kinetiku procesa je determinirana dilatometrijskim krivuljama. Procijenjeni su kvantitativni transformacijski izrazi i koefi cijent toplinskog širenja kaljenih i propuštenih struktura (austenit, perlit, mertenzit, sorbit). Napravljena je analiza utjecaja trajanja popuštanja na tvrdoću popuštenog čelika. Preporučena je funkcija koja udružuje tvrdoću i trajanje propuštanja (brzina zagrijavanja) u tehnološkom procesu temeljena na kratkotrajnom djelovanju izvora topline (npr. tretman laserom)

Effect of Antimony and Cerium on the Formation of Chunky Graphite during Solidification of Heavy-Section Castings of Near-Eutectic Spheroidal Graphite Irons

Thermal analysis is applied to the study of the formation of chunky graphite (CHG) in heavysection castings of spheroidal graphite cast irons. To that aim, near-eutectic melts prepared in one single cast house were poured into molds containing up to four large cubic blocks 30 cm in size. Four melts have been prepared and cast that had a cerium content varying in relation with the spheroidizing alloy used. Postinoculation or addition of antimony was achieved by fixing appropriate amounts of materials in the gating system of each block. Cooling curves recorded in the center of the blocks show that solidification proceeds in three steps: a short primary deposition of graphite followed by an initial and then a bulk eutectic reaction. Formation of CHG could be unambiguously associated with increased recalescence during the bulk eutectic reaction. While antimony strongly decreases the amount of CHG, it appears that the ratio of the contents in antimony and cerium should be higher than 0.8 in order to avoid this graphite degeneracy

Mechanical properties of AlSi10Mg alloy fabricated by laser melting deposition and improvements via heat treatment

Process optimization and heat treatment of AlSi10Mg aluminum alloy parts fabricated by laser melting deposition (LMD) based on coaxial powder feeding are conducted in this paper to improve manufacturing quality. The microstructures and mechanical properties of the LMD-built AlSi10Mg alloy parts are systematically investigated. Experimental results show the relative density of the block samples increase to 99.2% without larger pores and cracks after process optimization. The sample microstructures are found to display directional rapid solidification characteristics, with the Al-Si eutectic microstructure containing three microstructures being cellular, columnar dendrites and divergent dendrites. With solution and artificial aging heat treatments, Si atoms are rejected from the supersaturated Al matrix to form small Si granular particles. The heat treated samples display a uniform microstructure without heterogeneities and the microhardness remains stable at 118 HV. When the as-built sample is heat treated for solution time 2h, tensile strength increases from 292 MPa to 342 MPa due to the formation of strengthening phase Mg2Si